1. Field of the Invention
The present invention relates generally to devices and tools for the measurement of downhole environmental parameters during oil and gas drilling operations. The present invention relates more specifically to a downhole drilling efficiency sensor for use with oil and gas drilling operations that accurately measures drilling parameters at or near the drill bit in order to increase the effectiveness and productivity of the drilling operation.
2. Description of the Related Art
U.S. Pat. No. 4,662,458 issued to Ho entitled Method and Apparatus for Bottom Hole Measurement and commonly assigned with the present application describes a downhole tool with strain gauges and includes measurements for weight-on-bit (WOB), torque-on-bit (TOB), bending-on-bit (BOB), and side forces.
U.S. Pat. Nos. 4,821,563 and 4,958,517, both issued to Maron and both entitled Apparatus for Measuring Weight, Torque, and Side Force on a Drill Bit, each describe an apparatus that includes strain gages located in radial holes in the wall of the drill collar sub. The strain gages are position in a non-symmetrical arrangement.
U.S. Pat. No. 5,386,724 issued to Das et al. entitled Load Cells for Sensing Weight and Torque on a Drill Bit While Drilling a Well Bore also describes the use of an array of load cells made up of strain gages for measuring weight and torque parameters. The Das et al. disclosure includes a recent review of the relevant art and a description of selected methods for calculating strain using strain gages of the type employed herein and is therefore cited and incorporated by reference herein in its entirety.